LUK

DMFs and Bolt requirements

LuK’s Dual Mass Flywheel part numbers will be, where possible, sold with the relevant bolts. However, for many DMFs, different bolts are required depending on the vehicle model.
LuK therefore also offers sets of bolts appropriate for the vehicle on which the DMF will be used.                                                                                   

What bolts are needed?

Due to continuous, strong alternating loads, specially designed bolts are used to secure flywheels. These are usually stretch bolts or bolts with microencapsulation. Stretch bolts have an anti-fatigue shaft that only covers around 90% of the thread core diameter. When tightened to the torque specified by the vehicle manufacturer the stretch bolt becomes an elastic bolt. The elasticity of the stretch bolt means it can be stretched right up to the elastic limit.

As they do not possess these properties, normal set screws would break after a certain amount of time due to material fatigue, even if they were strong enough in their design.

When should they be replaced?

Bolts that have already been used must not be used again. These snap when they are tightened. In addition, their sealing and gripping properties are no longer effective.

Key Points to Remember:

• DMFs either sold with bolts and without bolts
• DMF bolt fitting kits also sold separately
• Specifically designed bolts to be used to secure flywheels
• Normal set screws are not adequate
• Bolts that have been used must not be used again

FPS currently stock 390 DMF’s without bolts, 53 DMFs with bolts and 66 DMF bolt fitting kits.

Top selling DMF bolt fitting kits, and the applications they fit can be seen below: